Many electronic devices use backlights to provide illumination for displays and other components. Backlights commonly use a lightguide that transmits light from a light source along an extent of the backlight. It is desirable for the backlight to provide substantially uniform brightness in the viewing areas with few observable defects. To soften or mask non-uniformities in brightness and other defects, a light scattering element, such as a diffuser, may be used. However, such scattering elements typically direct light away from a preferred viewing axis and require higher power output to achieve the same level of brightness.
The efficient use of light to illuminate keypads and displays is particularly important in battery powered portable devices because illumination of the device consumes a relatively large percentage of the device power budget. Light extractors have been used to extract light from lightguides and to enhance the uniformity of the lightguide brightness.
There is a need for lightguides that can enhance illumination, reduce observable defects, and/or reduce power requirements of a variety of devices. The present invention fulfills these and other needs, and offers other advantages over the prior art.